Stereoscopic visualization techniques are used to create the impression of a three-dimensional scenario in a viewer of a stereoscopic display. The viewer experiences the three-dimensional impression in that the viewer's eyes perceive different images.
Interaction with three-dimensional virtual objects in a three-dimensional virtual scenario requires the input of three translational degrees of freedom because, compared to a two-dimensional scenario, the three-dimensional scenario also has a dimension of depth. The input of three degrees of freedom requires special interaction devices and/or methods since conventional interaction devices, such as a so-called computer mouse or a so-called trackball, provide only two translational degrees of freedom.